Analytical Chemistry Chemical Cytometry Quantitates Superoxide

Anal. Chem. 2010, 82, 6756–6763
An Enzymatic Microreactor Based on Chaotic
Micromixing for Enhanced Amperometric
Detection in a Continuous Glucose Monitoring
Application
Byeong-Ui Moon, †,‡ Sander Koster, § Klaas J. C. Wientjes, † Radosław M. Kwapiszewski, |
Adelbert J. M. Schoonen, † Ben H. C. Westerink, † and Elisabeth Verpoorte* ,‡
Biomonitoring and Sensoring, Pharmaceutical Analysis, Department of Pharmacy, University of Groningen, Antonius
Deusinglaan 1, P.O. Box 196, 9700 AD Groningen, The Netherlands, TNO Quality of Life, Utrechtseweg 48,
3700 AJ Zeist, The Netherlands, and Department of Microbioanalytics, Faculty of Chemistry, Warsaw University of
Technology, Noakowskiego 3, Warsaw, 00-664, Poland
The development of continuous glucose monitoring systems
is a major trend in diabetes-related research. Small,
easy-to-wear systems which are robust enough to function
over many days without maintenance are the goal. We
present a new sensing system for continuous glucose
monitoring based on a microreactor incorporating chaotic
mixing channels. Two different types of chaotic mixing
channels with arrays of either slanted or herringbone
grooves were fabricated in poly(dimethylsiloxane) (PDMS)
and compared to channels containing no grooves. Mixing
in channels with slanted grooves was characterized using
a fluorescence method as a function of distance and at
different flow rates, and compared to the mixing behavior
observed in channels with no grooves. For electrochemical
detection, a thin-film Pt electrode was positioned at the
end of the fluidic channel as an on-chip detector of the
reaction product, H 2O2. Glucose determination was
performed by rapidly mixing glucose and glucose
oxidase (GOx) in solution at a flow rate of 0.5 µL/min
and 1.5 µL/min, respectively. A 150 U/mL GOx
solution was selected as the optimum concentration
of enzyme. In order to investigate the dependence of
device response on flow rate, experiments with a
premixed solution of glucose and GOx were compared
to experiments in which glucose and GOx were reacted
on-chip. Calibration curves for glucose (0-20 mM, in
the clinical range of interest) were obtained in channels
with and without grooves, using amperometric detection
and a 150 U/mL GOx solution for in-chip reaction.
1. INTRODUCTION
Diabetes mellitus is a widespread disease causing heart
disease, weight loss, blurry vision, neurological disorders, and
* Corresponding author. E-mail: e.m.j.verpoorte@rug.nl, Telephone: +31-50-
363-3337; fax: +31-50-363-7582.
† Biomonitoring and Sensoring, University of Groningen.
‡ Department of Pharmacy, University of Groningen.
§ TNO Quality of Life.
| Warsaw University of Technology.
6756 Analytical Chemistry, Vol. 82, No. 16, August 15, 2010
even death. 1 Proper management of blood glucose is thus of
crucial importance for diabetic patients. The conventional way
blood glucose determinations are carried out involves the
finger-prick method. Usually, diabetic patients measure their
own blood glucose several times per day by applying a drop of
blood to a portable device. However, this intermittent monitoring
does not yield the full range of information necessary to
effectively control glucose levels 24 h a day. The current
research trend is thus toward real-time in vivo monitoring over
longer periods (days). 2-5 Type 1 diabetic patients in particular
could benefit from a portable glucose sensor to keep their
glucose values within a reasonable range. Theoretically, a
portable glucose sensor could include an insulin pump in a
feedback loop to serve as an artificial pancreas.
Electrochemical detection is commonly used for glucose
analysis. 6 The advantages of electrochemical detection include
sensitivity and ease of interfacing with detection electronics.
Several reports incorporating electrochemical detection on a
microchip have been published for the detection of glucose. 7-9
The principle of the enzymatic reaction involved is shown in
eqs 1 and 2. Glucose, O2 and glucose oxidase (GOx) react to
generate hydrogen peroxide (H2O2) at concentrations proportional
to the original glucose concentrations. The H2O2
is then oxidized under applied potential into O2 and H + , with
the resulting electrons being recorded as an electrical
current.
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(9) Yamaguchi, A.; Jin, P.; Tsuchiyama, H.; Masuda, T.; Sun, K.; Matsuo, S.;
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10.1021/ac1000509 © 2010 American Chemical Society
Published on Web 07/21/2010